PROJECT SUMMARY Liver transplantation is the only definitive therapy for end-stage liver disease. A significant pool of liver donors comes from donation after cardiac death (DCD). The challenge with DCD donors is the prolonged warm ischemia that can result in significant liver dysfunction, thus leading to the development of early allograft dysfunction (EAD) or even primary non-function (PNF) in the recipient. Development of a therapeutic agent to preserve DCD liver donor integrity would have significant therapeutic value in reducing EAD/PNP during or after a liver transplant. Previously we identified MG53 as an essential component of cell membrane repair. In this proposal, we present promising data to support the scientific premise that muscle-liver crosstalk via MG53 as a myokine constitutes an integral part of hepatocellular protection. While the liver does not express endogenous MG53 protein, MG53 can translocate from circulation to target injured hepatocytes during the acute phase of hepatic injury. Biochemical and live cell imaging studies revealed that MG53 can interact with MLKL to preserve hepatocellular integrity. Using the normothermic ex-vivo liver perfusion (NEVLP) platform, we found that the presence of recombinant human MG53 (rhMG53) protein in the perfusion solution could improve liver donor integrity. We thus envision that rhMG53 can function as a novel biological reagent to improve donor organ preservation and function during liver transplantation. Studies designed in this project focus on defining the physiological role of muscle-derived MG53 in hepatoprotection and elucidating the underlying mechanisms of MG53-mediated control of MLKL signaling in injured hepatocytes (Aim 1); and establishing the safety and efficacy of using rhMG53 to preserve the integrity of DCD liver donors during NEVLP and to improve liver transplant outcomes in animal models (Aim 2).